My 7d2 with the native EF 24-105 f/4 L just fits into my camera bag. My EOS R with adapter and the same EF 24-105 f/4 L just fits into my camera bag. I surmise by this that there's almost no difference in the size even with the adapter on the R*. Additionally, the EF to RF adapter that I have is pure passthrough and makes absolutely no difference optically or electrically, allowing the lenses to perform identically on either camera. So the statement you made isn't universally true. I would urge people to do a little research about the EF - RF setup before claiming otherwise. * I think overall, it adds about 5mm over the length of the 7d2, but this is exacerbated by the EVF which sticks out further than the viewfinder on the 7d2**. **Actually, I just checked, and overall, the EOS R is just over 1cm longer than the 7d2 with the adapter and lens mounted. EOS R + EF to RF adapter + 24-105 Lens EOS 7d2 + 24-105 Lens As you can see, the EOS R EVF sticks out back from the camera further than the 7d2 viewfinder does.